A patch clamp technique in electrophysiology is known as a method for measuring an ion channel that is present in a cell membrane. With this patch clamp technique, various functions of the ion channel have been elucidated. The function of the ion channel is of keen interest in cytology and is applied to development of drugs.
Meanwhile, however, a measuring method by the patch clamp technique requires an extremely high skill of inserting a fine micropipette into one cell with high accuracy. Therefore, this technique requires a skilled operator, so that it is not suitable for cases that require high-throughput measurement.
Therefore, an automated system that does not require the insertion of a micropipette into an individual cell and is capable of automatically fixing and measuring a cell merely by reducing a pressure has been developing.
As shown in FIG. 9, a conventional cell electrophysiological sensor includes mounting substrate 1 made of resin, sensor chip 3 that is made of silicon and inserted into through hole 2 of mounting substrate 1, and electrodes 4 and 5 disposed on the upper and lower parts of mounting substrate 1.
Furthermore, sensor chip 3 has conducting hole 6. Electrolytic bath 7 disposed inside through hole 2 of mounting substrate 1 and on mounting substrate 1 and electrolytic bath 8 disposed at the lower part are filled with an electrolytic solution. Electrolytic baths 7 and 8 are partitioned by mounting substrate 1 and sensor chip 3.
In this cell electrophysiological sensor, cell 9 is filled in electrolytic bath 7. Cell 9 can be sucked and trapped in an opening part of conducting hole 6 by applying a pressure from the upper part or reducing a pressure from the lower part of conducting hole 6. Then, for example, a drug is provided from the upper part of cell 9, and the potential difference between electrolytic baths 7 and 8 is measured by electrodes 4 and 5. Thus, the pharmacological reaction of cell 9 can be determined (see, for example, Patent Document 1).
Conventional sensor chip 3 has a problem that the measurement accuracy of the cell electrophysiological sensor is low. The reason therefor is that air bubbles 10 tend to be deposited in the vicinity of conducting hole 6 of sensor chip 3.
That is to say, as shown in FIG. 9, a conventional cell electrophysiological sensor is produced by directly inserting sensor chip 3 into mounting substrate 1 and fixing it with, for example, an adhesive agent. In the cell electrophysiological sensor, the outer periphery of sensor chip 3 is surrounded by the inner wall of through hole 2 of mounting substrate 1. Since mounting substrate 1 is hydrophobic, air bubbles tend to be deposited inside through hole 2. When air bubbles are deposited in the vicinity of conducting hole 6 of sensor chip 3, the adhesion between cell 9 and an opening part of conducting hole 6 is reduced or continuity between the upper and lower parts of conducting hole 6 is prevented. As a result, the measurement accuracy of the cell electrophysiological sensor is reduced.
[Patent Document 1] Japanese Translation of PCT Publication No. 2002-518678